This paper describes cryogenic broad-band amplifiers with very low power consumption and very low noise for the 4-8-GHz frequency range. At room temperature, the two-stage InP-based amplifier has a gain of 27 dB and a noise temperature of 31 K with a power consumption of 14.4 mW per stage, including bias circuitry. When cooled to 15 K, an input noise temperature of 1.4 K is obtained at 5.7 mW per stage. At 0.51 mW per stage, the input noise increases to 2.4 K. The noise measurements have been repeated at different laboratories using different methods and are found consistent.

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The performance of broadband, Low-Noise, Low DC consumption cryogenic amplifiers was studied in detail with emphasis to minimize the power consumption and optimize the amplifier performance at cryogenic temperature. A general approach used in the modeling and amplifier design can help to minimize the power consumption and optimize the performance of the amplifier. A noise temperature below 6K and 25 dB gain was experimentally obtained in the frequency range 4-8 GHz with total power consumption of 4 mW with commercial GaAs transistor.